1. Field of the Invention
The invention relates to a displacement machine for compressible media having at least four delivery spaces arranged in a fixed housing, in the case of four delivery spaces each housing half having two delivery spaces which are offset by about 180.degree. with respect to one another and extend in a spiral shape from an inlet to an outlet, and each delivery space being allocated a displacement body which fits into the latter and is held, as a spiral-shaped strip, perpendicularly on a disk-shaped rotor which can be driven eccentrically with respect to the housing and for the guidance of which a second eccentric guiding arrangement arranged at an interval from a first eccentric drive arrangement is provided in the housing, there being provided on the rotor a compensating means for the flexible accommodation of any length differences between delivery space and displacement body.
2. Discussion of Background
Displacement machines on the spiral principle are known, for example, from DE-C3-2,603,462 which corresponds to U.S. Pat. No. 3,989,422. These machines are distinguished by a virtally pulsation-free delivery of the gaseous working medium comprising air or an air/fuel mixture and can therefore also be employed with advantage for the purpose of supercharging internal combustion engines. During the operation of a displacement machine of this kind, working as a compressor, a plurality of approximately crescent-shaped working spaces which move through the delivery chamber from a working medium inlet to a working medium outlet are enclosed along the delivery chamber between the spiral-shaped displacement body and the two cylinder walls of the delivery chamber as a result of the different curvature of the spiral shapes, the volume of said working spaces decreasing constantly and the pressure of the working medium being correspondingly increased. The displacement bodies are formed by spiral-shaped strips which are held essentially perpendicular on the disk-shaped rotor and have a relatively great axial length in relation to their thickness. Similar conditions apply on the side of the fixed housing, where spiral-shaped, strip-like webs remain between the delivery chambers, said webs having a relatively great length in the axial and in the peripheral direction in relation to their wall thickness.
A precise rolling contact of a displacement body on the spiral principle by virtue of a translational circular motion is achieved by means of a double crank mechanism, such as that known, for example, from DE-A-3,230,979 and in which one crank drives and the second crank guides. In order to be able to compensate length differences between the two points of application of the drive and the guide arrangements, this known solution envisages a transmission member which can be displaced longitudinally, i.e. in the direction of the line connecting the points of application. This transmission member comprises a holding member which is held displaceably in the guide arrangement of the rotor and can be a slider which is displaceable in a parallel guide. The parallel guide comprises one of the two bearings of the guide arrangement, via which any compensation of differences in expansion can thus take place.
Another solution to this problem is described in DE-A-3,107,231. To avoid impermissibly high loads, which may occur by reason of tolerance summation in production or by reason of differential thermal expansion between the two points of application at the rotating rotor, a bearing arrangement provided with an elastic bedding is provided at at least one of the points of application, preferably at the point of application of the guide device. This elastic bedding can, for example, be formed by a rubber-elastic ring which rests between bearing outer ring and bearing eye.